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Coordinated observations of the effect of consecutive HSS pulses on relativistic electron enhancement
  • +12
  • Afroditi Nasi,
  • Ioannis Daglis,
  • Christos Katsavrias,
  • Ingmar Sandberg,
  • Wen Li,
  • Yoshizumi Miyoshi,
  • Shun Imajo,
  • Takefumi Mitani,
  • Tomoaki Hori,
  • Satoshi Kasahara,
  • Shoichiro Yokota,
  • Kunihiro Keika,
  • Iku Shinohara,
  • Ayako Matsuoka,
  • Yoshiya Kasahara
Afroditi Nasi
National and Kapodistrian University of Athens

Corresponding Author:[email protected]

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Ioannis Daglis
National and Kapodistrian University of Athens
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Christos Katsavrias
National and Kapodistrian University of Athens
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Ingmar Sandberg
Space Applications and Research Consultancy
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Wen Li
Boston University
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Yoshizumi Miyoshi
Nagoya University
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Shun Imajo
Kyoto University
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Takefumi Mitani
Japan Aerospace Exploration Agency
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Tomoaki Hori
Nagoya University
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Satoshi Kasahara
The University of Tokyo
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Shoichiro Yokota
Osaka University
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Kunihiro Keika
The University of Tokyo
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Iku Shinohara
Japan Aerospace Exploration Agency
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Ayako Matsuoka
Kyoto University
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Yoshiya Kasahara
Kanazawa University
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Abstract

During the second half of 2019, a series of recurring, moderate geomagnetic storms (Dst ≈ - 70 nT) emerged after a sequence of high-speed solar wind streams (Vsw ≥ 600 km/s) impacted the magnetosphere. During one of these storms, intense substorm activity was also recorded (SML ≈ - 2000 nT on August 31 and September 1), as well as a longer-lasting solar wind pressure pulse. We investigate this series of events, using particle measurements from three missions that recorded significant enhancements of relativistic electron fluxes: the Van Allen Probes, Arase and Galileo 207 & 215 satellites. We use both the flux intensity and the phase space density (PSD) of electrons, along with interplanetary parameters and information on ultra-low frequency (ULF) and chorus wave activity for a detailed analysis of this event. Our study demonstrates the importance of substorm injections, even during moderate or weak geomagnetic storms. The presence of seed electrons at L* = 4-5, in addition to intense ULF and chorus wave activity, seems to result in very efficient electron acceleration to relativistic and ultra-relativistic energies. This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870437 for the SafeSpace project.